The present invention relates to an optical semiconductor module.
A conventional optical semiconductor module 100 has a TO type CAN case 102, light-emitting element 104, optical fiber 106, ferrule 108, and support member 110. The light-emitting element 104 is accommodated in the case 102. The optical fiber 106 is optically coupled to the light-emitting element 104. The ferrule 108 supports the optical fiber 106. The support member 110 supports the ferrule 108. The support member 110 has a cylindrical shape extending in a direction along the optical axis of the light-emitting element 104, and is fixed to the side surface of the CAN case 102 through adhesive 112. This configuration enables the optical fiber 106 to optically couple to the light-emitting element 104.
The inventor has made studies for developing a smaller version of an optical semiconductor module. As the result of these studies, the inventor found a demand for decreasing the cross sectional area of the optical semiconductor module in a surface perpendicular to the optical axis particularly in this technical field.
It is, therefore, an object of the present invention to provide an optical semiconductor module having a structure allowing the above downsizing.
The inventor made further studies in order to realize this object.
First, the inventor made studies on the roles of components composing the conventional optical semiconductor module. The TO type CAN case accommodates an optical semiconductor element, such as a semiconductor laser or a semiconductor light-receiving element. A support member serves to optically couple an optical fiber to this semiconductor light-emitting element or semiconductor light-receiving element. The support member has an insertion hole for defining a direction in which a ferrule holding the optical fiber is inserted. The direction of the ferrule is determined by the angle at which the CAN case is inserted in the insertion hole of the support member. In the support member, the inner diameter of the cylindrical portion is determined to be associated with the outer diameter of the CAN case. This structure enables the optical fiber to coincide with the optical axis of the light-emitting element when the support member is aligned with the CAN case.
Subsequently, in the optical semiconductor module with components exhibiting these roles, the inventor made studies on the shape of the optical semiconductor module in a cross section perpendicular to the optical axis. The inventor found as follows: the support member has a portion accommodating the CAN case inserted thereto. It is difficult to reduce the cross section of this portion in the optical semiconductor module as compared to the others of the optical semiconductor module. Therefore, what is needed is to reduce the cross sectional area of this portion in the optical semiconductor module.
The inventor continued the studies on a structure that implements the reduction, and eventually invented the following.
An optical semiconductor module according to the present invention comprises a mounting member, a first member, an optical semiconductor element, a second member, and an optical waveguide. The mounting member extends along a reference plain intersecting a predetermined axis. The first member has a tubular portion, first and second ends, said tubular portion extending in a direction of the predetermined axis, a first end being provided at one end of the tubular portion, and a second end being provided at the other end of the tubular portion. The first end is secured to the mounting member. The optical semiconductor element is arranged in the tubular portion of the first member such that its optical axis extends in a direction of the predetermined axis. The second member has a tubular portion extending in a direction of the predetermined axis, and is secured to the second end of the first member. The optical waveguide is provided to pass through in the tubular portion of the second member such that it is optically coupled to the optical semiconductor element.
Since the first member is secured to the mounting member, the mounting member and first member define a space for accommodating the optical semiconductor element. The second member defines a direction in which the optical waveguide extends. The second member is secured to the second end of the first member. This securing determines the direction in which the optical semiconductor element can be optically coupled to the optical waveguide.
Since the mounting member and first member define the accommodating space for the optical semiconductor element, this configuration does not need any support member surrounding a CAN case therewith as in the conventional optical semiconductor module. Therefore, the optical semiconductor module is provided with a structure enabling the downsizing thereof.
In the present invention, one or more features that will be described below can be combined with each other arbitrarily.
The optical semiconductor module according to the present invention can further comprise a ferrule. The ferrule can be arranged in the tubular portion of the second member, and can be secured thereto. The optical waveguide may include an optical fiber supported by the ferrule.
The ferrule is guided by the tubular portion, and is arranged in the tubular portion of the second member while supporting the optical fiber. This configuration enables the optical fiber to be optically coupled to the optical semiconductor element. Since the ferrule is secured to the second member, the optical coupling becomes stabilized.
The optical semiconductor module according to the present invention further comprises a third member having a tubular portion and a pair of openings. The tubular portion of the third member extends in a direction of the predetermined axis, and accommodates the second member and the ferrule. The openings are arranged at two ends of the tubular portion. The optical fiber passes through one opening of the pair of openings to the ferrule.
The second member and ferrule are arranged in the tubular portion of the third member, and are protected by the tubular portion. Since the optical fiber passes through one opening of the pair of openings, the third member guides the optical fiber so as to extend toward the ferrule, thereby defining a range in which the optical fiber can be bent. This structure suppresses an unexpected force from being applied to the optical fiber at a position where the optical fiber is inserted in the ferrule.
In the optical semiconductor module according to the present invention, the ferrule has first and second end faces. The optical fiber can be arranged to extend from the first end face toward the second end face of the ferrule. The ends of the optical fiber appear at both the first and second end faces, respectively. Hence, one of the first and second end faces can be optically coupled to the optical semiconductor element. The other one of the first and second end faces can be optically coupled to another optical fiber.
The optical semiconductor module according to the present invention further comprises a sleeve in which the ferrule is inserted. The second member has a depressed portion provided in an inner wall surface of the tubular portion. The sleeve can be arranged in the depressed portion of the second member.
The sleeve is accommodated in the depressed portion provided in a predetermined position of the second member, thereby determining the position of the ferrule.
In the optical semiconductor module according to the present invention, the tubular portion of the second member has first and second portions adjacent to each other in a direction of the predetermined axis. The first portion accommodates the ferrule. The second portion is provided so as to arrange another ferrule. Another ferrule holds another optical fiber that should be optically coupled to the optical fiber. When the other ferrule is inserted in the second member, the other optical fiber is optically coupled to the optical semiconductor element. The inner wall surface of the tubular portion guides the other optical fiber which is being inserted, and the sleeve enables the optical alignment of the other optical fiber.
The optical semiconductor module according to the present invention further comprises a lens provided between the optical waveguide and the optical semiconductor element. This lens enables the optical tight coupling between the optical semiconductor element and the optical waveguide.
In the optical semiconductor module according to the present invention, the optical semiconductor element can be either one of a light-emitting element and a light-receiving element. If the optical semiconductor element is a light-emitting element, it can provide an optical signal to the optical fiber. If the optical semiconductor element is a light-receiving element, it can receive the optical signal from the optical fiber and convert it into an electrical signal.
In the optical semiconductor module according to the present invention, the first member is secured to the mounting member at an annular connecting portion. The annular connecting portion is so formed as to surround a straight line on the optical axis of the optical semiconductor element. Since the annular connecting portion is provided to be highly symmetric with respect to the optical axis, it averages displacement of the first member in securing it.
In the optical semiconductor module according to the present invention, the mounting member can be included in a cylindrical shape, having the center axis perpendicular to the reference surface and a cross section having a diameter of 4 mm or less. With the structures of the optical semiconductor module that has been already described in this specification and will be described hereinafter, optical semiconductor modules that can be accommodated in a cylindrical shape with a diameter of 4 mm or less can be realized.